Hydraulic power transmission with flow control by-pass valve



BY PASS VOLUME Fug/E R. L. TWEEDALE HYDRAULIC POWER TRANSMISSION WITH FLOW CONTROL BYPASS VALVE Filed Dec. 26, 1944 PRESSURE 0 Z 2 LL, 78 u 3 7 6 44 4 We 56 46 5 Z 30 Fig] H 5 U INVENTOR.

Patented Aug. 17, 1948 HYDRAULIC POWER TRANSMISSION WITH FLOW CONTROL BY-PASS VALVE.

Ralph L. Tweedaie, Birmingham, Mica, aslignor to Vlckera Incorporate poratlon of Michigan (1, Detroit, Mich, a cor- Applica tion December 28, 1944, Serial No. 569,827

This invention relates particularly to those of the type compris ng two or more fluid pressure energy translating devices,

one of which may function as a pump and an-.

of the reel. Likewise, if a constant tension is maintained on the reeled material increasing in diameter, a progressively increasing torque must be applied tothe reel.

In a hydraulic transmission for driving a reel comprising a fixed displacement pump and motor driving the reel, the product of pressure and volume should be a constant. As the material being wound upon the reel increases in diameter and the pressure rises, the volume of fluid to the motor driving the reel should decrease, not along a straight-line relation but by a hyperbolic relation.

It is an object of the present invention to provide, for use in a hydraulic transmission coniprising a hired displacement pump and motor for driving a reel, a flow regulating device which will maintain a constant uniform tension upon a strip of material being wound upon a reel as it Jncreases in diameter.

It is also an object of this invention to provide for use in a hydraulic transmission, as above mentioned, a pressure responsive throttle valve conto power transmissions.

. 130lalms. (ciao-s3) ing drawing wherein a preferred form 01' the structed and designed to give a predetermined in-' V creased bleed-on. of pump volume in response to an increase in motor pressure to establish the required hyperbolic relationship between motor pressure and flow through, or displacement of, the motor.

It is a further object of this invention to provide foruse in a hydraulic transmission, as above mentioned, a simply constructed and economically manufactured flow regulating valve which will decrease the speed 01 the motor driving a reel in response to an increase of motor pressure and torque as the diameter of the material being wound on the reel increases.

Further objects and advantages of the present invention will be apparent from the following description, reference being hadto the accompanypresent invention is clearly shown.

In the drawing:

Figure 1 is a diagrammatic view of a power transmission system incorporating a preferred form of the present invention.

Figure 2 is a plot 01' fluid flow changes with pressure changes.

Figure 3 is a plot 01' valve with pressure changes.

Referring now to Figure 1, there is illustrated a pump ill of the fixed displacement type, which may be driven by an electric motor l I, which has a suction conduit I: connected to a tank i 4 and a pump delivery conduit i8 connected to the inlet port l8 oi a'iiow regulating valve 20 which also has an outletport 22, a bypass port 24 and, in its preferred form, a venting port 26. Connected to the outlet port 22 of valve 20 is a supply conopening changes duit 28 connected to a motor 30 having also a return conduit 32 connected to the tank I4. The motor all drives a reel 34 of winding a strip of material thereon.

A conduit 38 connects the venting port 26 with a suitable two-way valve 88. and a conduit 40 connects valve 38 with the tank l4. The twoway valve 38, 20 closed to direct fluid from pump ill to motor 80 to start said motor, or, when opened, will open valve 2!! completely to unload pump ill to tank l4 to stop motor 30. v 1 a The flow regulating valve 20 is comprised of a housing having a longitudinal stepped bore 42 communicating with the inlet port it, outlet port 22, bypass port 24 and venting port 26. Shiftable within bore 42 is a throttle vlave 44 comprising a piston 46 connected to which is a stem 48 tapered at a point 50 to rest on a seat 52 formed within the bore 42, The valve 44 has tapered grooves 53 and a centrally drilled passagezvay584 and a restricted passageway 56in the pis- Valve 44 when positioned in bore 42 forms a lower chamber 58 on the underside of piston 46 and an upper chamber between the upperside of piston 48 and the inner side of an end cap 62.

The passageway 56 in piston 45 forms a com-- munication between chamber 58 and chamber 60. A spring 64 of predetermined light tension is located in the upper chamber 60 abutting the upper side of piston 46 and the inner side of end cap 62 and tends to bias valve 44 to the closed position.

When seated, the valve blocks communication between inlet port l8 and bypass port 24.

used for the purpose when closed, will hold the valve- An exhaust chamber 55 formed in bore 42 be-' tween seat 52 and-bypass port 24 together with a conduit 51 provide passage for fluid bypassed through the seat 52. V

A pilot valve 55 is located in the upper chamber 68 and has a conical surface 58 at one end designed to seat on the upper end of passageway 54 of valve 44 and has a centrally drilled passageway 10. A spring 14 of predetermined resistance, abutting the upper end of pilot valve 56 and an adjustable screw 16, and located within a bore of end cap 52, tends to bias valve 55 to the seated position. The pilot valve 65 is shiftable within bore 15. Passageway I0, connecting with bypass port 24, tends to act as. a drain for any fluid seepage in bore 15 which would tend to disturb the effective operation of pilot valve 86. A protective cap I8 is threaded over the adjustable screw 15 to protect the setting of spring 14 which is originally set according to the diameter of reel 34 in order to provide the correct motor speed required duringthe winding operation.

In operation, with the pump Ill running, the two-way valve 38 is shifted to block communication between venting port 01' valve 20 and tank l4. This blocks egress from chamber 50,

and the pressure therein will equalize with that in chamber 58, thus permitting spring 54 to close valve 48. Fluid from tank i4 is withdrawn through conduit l2 by pump 18 and delivered into conduit it to the inlet port ill of valve 20 and through outlet port 22 and conduit 28 to motor 30 which drives reel 34, the return fluid from motor 30 returning to tank i4 by means of conduit 32.

At this stage of the operation, because the small diameter of the material winding on reel 34 creates a low torque, the pressure in conduits i6 and 28 is low, and the reel is being operated by motor 30 at the highest possible speed. Fluid under pressure entering inlet port I8 of valve 28 is blocked from communication with bypass port 24 because of valve 58 being seated on seat 52. Fluid under pressure entering chamber 58 also enters upper chamber 50 by means of passageway 58 in piston 46 and acts on pilot valve 56 at surface 68. Chamber 8|] is blocked from communication with bypass port 24 because of pilot valve 55 resting on the seat formed in the upper end or passageway 54 in valve 44. The force exerted on the upper side of piston 45 is greater than the force exerted on its underside because of a slightly greater area on the upper side of piston 45, tending to keep valve 53 seated.

As the diameter of the winding strip of material increases on reel 34 causing an increase in torque of motor 38 which causes an increase in pressure, this increase of pressure will also react on pilot valve 56 at surface 58 by means of passageway 58 in piston 48. With each increase of pressure, the resistance of spring I4 will be slightly overcome, and pilot valve 58 will raise,

in chamber 58 on the upper side of piston 48, valve 44 will raise slightly, unseating valve 58 from seat 52, allowing fluid to be bypassed at a predetermined rate from pump Ill to tank I4 through seat 52, exhaust chamber 55, bypass port 24 and conduit 61.

As the pressure at motor 30, which is equal to the pressure at pump i0, continues to increase because 01 the increase in diameter of the strip of material being wound on reel 34, the same presure increase will react on pilot valve 86 permitting valve 44 to continue to raise. The tapered grooves 53 of valve 44 are designed to permit an increasing amount of fluid from pump III to be bypassed to tank M as the pressure at motor 30 continues to increase- As the amount of fluid being bypassed from pump 10 to tank l4 increases, the speed of motor 30 is proportionately decreased, thus maintaining a constant tension upon the strip of material being wound upon reel 34.

Considering the operation in more detail, it

should be noted that pilot valve 66 rests upon main valve 44 so that the position of main valve 44 effectively determines the compression of pilot valve spring 14. In other words, as main valve 44 lifts, it progressively increases the compression of pilot valve spring 14 and thus raises the pressure at which pilot valve 66 opens. The curvature of the tapered grooves 53 is predetermined in accordance with the characteristics of spring 14 and the laws of fluid flow so that for any pressure in motorconduit 28 there will be a predetermined area of opening through the valve seat 52. This is chosen so as to achieve the desired performance results as to the relationship between the speed of the motor 30 and the operating pressure thereof.

There is plotted in Figure 2 an example of a relationship between motor pressure and the volume of fluid bypassed through seat 52 which is in the general form of a. hyperbola based on the relationship that the difference between the fixed pump displacement and the bypass volume when multiplied by the pressure equals a constant. Because the oriflce formed by seat 52 and tapered grooves 53 is not subject to a constant pressure, the area of grooves 53 at any given position of valve 44 must be chosen to take this factor into sure impressed across the valve orifice at greater openings of the valve 44, the curvature of grooves 53 can be made to produce any desired motor performance as the .real diameter progressively increases.

Commonly it is desired to maintain uniform tension and uniform linear speed on the strip material, and this relationship is easily achieved by proper computation as to the conformation of the grooves 53. It will thus be seen that any desired relationship between reel speed and torque may be easily maintained throughout a wide range of reel diameters.

When the winding operation has been completed, the control handle of valve 38 is shifted to connect venting port 28 of valve 2il-with tank H by means of conduits 3G and 40. Fluid under pressure entering chamber 58 and chamber'fill is permitted to leave chamber 60 by way of port 28 faster than it can enter chamber 60 due to the restricted passageway 56 in piston 48 which causes a pressure drop in chamber 60 and completely opens valve which will unload pump it to tank l4 and thus stop motor 30.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow. Although the invention has been shown to be suitable and adaptable for use in a hydraulic transmission for driving a reel comprising a fixed displacement pump and motor driving the reel, it may be successfully applied in a similar hydraulic transmission for driving any load device where similar results are desired. Thus, the invention may be applied in a hydraulic transmission containing a fixed displacement pump and motor driving a load device where it isdesired to drive the load device at varying and progressive speeds and torques but at substantially constant horsepower, or where a desired relationship between the speed or the driven load device and torque of the same is required in spite of a continuously varying load resistance,

or where the speed of the driven load device must change in a predetermined relationship in response to changes in torque.

Certain subject matter in common with the present invention is disclosed and claimed in a copending application of Warren Brown, Serial No. 569,826, filed December 26, 1944, title, Power transmission.

What is claimed is as follows:

1. In a hydraulic power transmission system for driving a reel and having a fixed displacement pump and a fixed displacement fluid motor, a

valve comprising a throttle as the sole restrictive means to bypass a variable portion oi the pump, delivery around the motor and having a predetermined relationship between its positional adjustment and is resultant opening area, and resiliently-loaded means responsive to the pressure required to drive the motor for controlling the positional adjustment of the throttle.

2. In a hydraulic power transmission system for driving a reel and having a fixed displacement pump and a'fixed displacement fluid motor, a valve comprising a throttle the entrance to which is in open and direct communication with the motor, and arranged to bypass a variable portion of the pump delivery around the motor and having a predetermined relationship between its positional adjustment and its resultant opening area, and resiliently-loaded means responsive to the pressure required to drive the motor for controlling the positional adjustment of the throttle.

3. In a hydraulic power transmission system ior driving a reel and having a fixed displacement pump and a fixed displacement fluidmotor, a valve comprising a, throttle the entrance to which is in open and direct communication with the motor, and arranged as the sole re strictive means to bypass a variable portion of the pump delivery around the motor and having a predetermined relationship between its positional adjustment and its resultant opening area,

and resiliently-loaded means responsive to the pressure required to drive the motor for controlling the positional adjustment of the throttle.

4. In a hydraulic power transmission system for driving a reel and having a fixed displacement pump and a fixed displacement fluid motor, a valve comprising a throttle as the sole restrictive means to bypass a variable portion of the pump lustment and its resultant opening area. and a.

resiliently-loaded pilot valve responsive tov the pressure required to drive the 'motor for controlling the positional adiustment oi the throttle.

5. In a hydraulic power transmission system {or driving a reel and having a fixed displacement pump and a fixed displacement fluid motor, a valve comprising a. throttle as the sole restrictive means to bypass a variable portion of the pump delivery around the motor and having a predetermined relationship between its positional adjustment and its resultant opening area. and aresiliently-loaded 'pilotvalve responsive to the pressure required to drive the motor. the pressure responseoi' which is varied with-the positional adjustment or the throttle, said pilot valve opening to cause an increased opening of the throttle valve. h

6. In a hydraulic power transmission system for driving a reel and having a fixed displace,- ment pump and a fixed displacement fluidmotor, a valve comprising a throttle as the sole re,-

strictive means to bypass a variable portion of the pump delivery around the motor andhaving a predetermined relationship between its positional adjustment and its resultantopening area.

and a resiliently-loaded pilot valve responsive to the pressure required to drive the motor, the

the motor and arranged to bypass a variable por- 1 tion of the pump delivery around the motor, a longitudinal stepped bore within which.- the throttleis shiftable and forming an upper and lower chamber in communication with each other, said throttle having a centrally drilled passageway, one end of which forms a seat, and a, resilientlyloaded pilot valve responsive to the pressure required to drive the motor and coacting with said seat, the pressure response of which is varied with the positional adjustment of the throttle, said pilot valve controlling the seat opening for controlling the opening of the throttle valve.

8. In a hydraulic power transmission system for driving a load device at speeds which are varied in response to changes in torque and having a fixed displacement fluid pump and motor, a valve having an inlet port, a motor port and an exhaust port and comprising a throttle the entrance to which is in open and direct communijustment oi the throttle, said pilot valve 7 controlling the seat opening for controlling the openin: of the throttle valve.

'9. In a hydraulic power transmission system for driving a load device at speeds which are varied in response to changes in torque and having a fixed displacement fluid pump and motor, a valve having an inlet port, a motor port and an exhaust port and a venting port to which is connected a manually-operated valve to direct fluid irom the pump to the motor to start and operate said motor or to completely bypass the motor and unload the pump in order to stop the motor. and

comprising a throttle the entrance to which is in open and direct communication with the motor and arranged to bypass a variable portion of the upper chamber and exhaust port, one end of which forms a seat. and a resiliently-loaded pilot valve responsive to the pressure required to drive the motor and coacting with said seat, the pressure response or which is varied with the positional adjustment of the throttle. said pilot valve controlling the opening of the seat for controlling the opening of the throttle valve.

10. In a hydraulic power transmission system for driving a load device at varying speeds and torques but at substantially constant horsepower and having a fixed displacement pump and a fixed displacement fluid motor; a valv comprising a throttle as the sole restrictive means to bypass a variable portion of the pump delivery around the motor and having a predetermined relationship between its positional adjustment and its resultant opening area, and resiliently-loaded means responsive to the pressure required to drive the motor for controlling the positional adjustment of the throttle.

able portion of the pump delivery around the mosponsive to the pressure required to drive the motor for controlling the positional adjustment 0!. the throttle.

12. In a hydraulic power transmission system for driving a load device at varying speeds and torques but at substantially constant horsepower and having a fixed displacement fluid pump and motor, a valve comprising a throttle the entrance to which is in. open and direct communication with the motor and arranged to bypass a variable portion of the pump delivery around the motor, a longitudinal stepped bore within which the throttle is shiftable and forming an upper and lower chamber in communication with each other, said throttle having a centrally drilled passageway, one end of which forms a seat, and a resiliently-loaded pilot valve responsive'to the pressure required to drive the motor and coactlng with said seat, the pressure response of which is varied with the positional adjustment of the throttle. said pilot valve controlling the opening of the seat for controlling the opening of the throttle valve.

13. In a hydraulic power transmission system for driving a load device at speeds which are varied in response to changes in torque and having a fixed displacement fluid pump and motor, a valve comprising a throttle the entrance to which is in open and direct communication with the motorand arranged to bypass a variable portion of the pump delivery around the motor, a longitudinal stepped bore within, which the throttle is shiftable and forming an upper and lower chamber in communication with each other, said throttle having a centrally drilled passageway, one end of which forms a seat, and a resiliently-loaded pilot valve responsive to the pressure required to drive the motor and coacting with said seat, the

pressure response of which is varied with the positional adjustment of the throttle, said pilot valve controlling theopening of the seat for controlling the opening of the throttle valve.

' RALPH L. TWEEDALE.

REFERENCES crrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS 

